Why Lake Erie is Under Attack from Algae Blooms

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Lake Erie is under attack from noxious algae blooms, and the
problem only looks likely to get worse if something isn't done to
reverse the trend, new research suggests.

In the summer of 2011, western
Lake Erie turned a noxious green, as a massive algae bloom
coated the surface and lapped up in mats along the shore. At its
peak, the bloom covered an area 2.5 times larger than that of any
Erie bloom on record, according to a study published today (April
1) in the Proceedings of the National Academy of Sciences.

Several factors converged to cause the bloom and may increasingly
do so in the future, said Anna Michalak, a study co-author and
researcher at the Carnegie Institution for Science at Stanford
University.

Fertilizing the algae

First, agricultural practices have changed in the past few years,
allowing for more fertilizer to run off from fields in the
surrounding region and end up in the lake, Michalak said. There,
the fertilizer feeds the growth of
algal blooms. The practices include increased use of
fertilizer, earlier application of the nutrients on bare ground
and less use of tillage, in which fertilizer or manure is worked
into the soil.

The first technique was intended to deliver fertilizer before
spring storms, so farmers would not have to pick a time to apply
fertilizer between rains, Michalak told OurAmazingPlanet.
However, the method hasn't worked as intended, due in part to
larger than expected storms. The second practice, avoiding
tillage of the soil, helps preserve nutrients in the earth, but
may increase the amount of fertilizer lost in large spring rains,
she said.

Perhaps more importantly, runoff was made worse by explosive
spring storms in 2011, which dropped a lot of rain in a very
short period of time and washed the fertilizer away, Michalak
said. In the lake, above-average temperatures also nourished the
algae. Furthermore, a lack of strong winds prevented the lake
from being mixed up, which normally makes algae sink to the
bottom and brings low-lying water up to the surface, she said.

Unfortunately for Lake Erie, climate change is expected to lead
to larger spring storms, warmer temperatures and fewer strong
winds in the future, Michalak said. Dealing with
climate change on a global level, then, could have an
important local effect, she said.

But agricultural practices are more easily changed. Methods that
lead to less fertilizer loss would help farmers, who must pay for
the nutrients, as well as the lake environment, she said.

Ugly and harmful

"We need management policies that are good for agriculture as
well as the lake ecology," Michalak said. "It doesn't do anybody
any good to have these nutrients flowing into the lake. It's
money being wasted by the farmers, and you are essentially
fertilizing the algae instead of fertilizing the crops."

The nutrients in the fertilizer runoff, particularly phosphorous,
feed the growth of a type of algae called
cyanobacteria. Besides being unsightly, the blooms hurt fish
in the lake by decaying and consuming massive amounts of oxygen,
creating
dead zones. But the cyanobacteria also pose a health hazard
to people; the predominant type of cyanobacteria present in the
2011 bloom, called Microcystis, produce a potent liver
toxin. The study found that levels of this toxin in the surface
of Lake Erie were up to 200 times above the limit deemed suitable
by the World Health Organization.

Invasive zebra mussels and quagga mussels have added to Lake
Erie's problems, as these organisms preferentially eat
phytoplankton that live in the lake and that normally compete
with cyanobacteria, Michalak said.

The 2011 bloom "was a significant one in Lake Erie and I agree
that it is unlikely to be unique," said Jan Ciborowski, a
researcher at the University of Windsor, Ontario, who wasn't
involved in the study.